import operator

def xor(value1, value2):
    """
    Exclusive-OR
    """
    result = ""
    if len(value1) <= len(value2):
        while len(value1) < len(value2):
            value1 = "0" + value1
    else:
        while len(value2) < len(value1):
            value2 = "0" + value2
    for i in xrange(len(value1)):
        if value1[i] != value2[i]:
            result += "1"
        else:
            result += "0"
    return result

